.donghua
  width: 150px
  height: 300px
  margin: 0 auto
  overflow: hidden
  background-image: url(../img/dongtu.webp)
  animation: donghua step-end 1s infinite

@keyframes donghua
  0%
    /* margin-left:0px;
    background-position: 0px 0px

  25%
    background-position: -150px 0px

  50%
    background-position: -300px 0px

  75%
    background-position: -450px 0px

  100%
    background-position: -600px 0px

.bigdonghua
  width: 100%
  height: 400px
  z-index: 1000
  position: relative
  margin-top: 100px

.bigdonghua-center
  width: 800px
  height: 200px
  margin: 0 auto
  display: flex